Fuel oil compositions containing a mixture of polymers to improve the pour point and flow properties

ABSTRACT

Mixtures containing (1) polymers of ethylene with polar monomers such as vinyl acetate, methyl methacrylate, ethyl fumarate, etc., and (2) homopolymers of ethylene or copolymers of ethylene with C3 - C18 alpha-olefins synergistically improve the pour point and flow characteristics of middle distillate petroleum oils.

United States Patent Hollyday, J1-

[ 51 May 9,1972

[54] FUEL OIL COMPOSITIONS CONTAINING A MIXTURE OF POLYMERS TO IMPROVETHE POUR POINT AND FLOW PROPERTIES [72] Inventor: William C. I-Iollyday,Jr., Watchung, NJ.

[73] Assignee: Esso Research and Engineering Company [22] Filed: Apr.22, 1969 [21] Appl.No.: 818,427

[52] U.S. Cl ..44/62, 44/66, 44/70 [51] ..C10I 1/16,Cl0l 1/18 [58] Fieldof Search ..44/62, 70, 80, 66', 252/56 R [56] References Cited 7 UNITEDSTATES PATENTS 3,254,063 5/1966 llnyckyj ..44/62X 2,379,728 7/1945Lieber et a1 ..44/62 X 2,615,845 10/1952 Lippincott et al.. ..44/62 X3,126,364 3/1964 llnyckyj ...44/62 X 3,250,599 5/1966 Kirk et a1 ..44/62FOREIGN PATENTS OR APPLICATIONS 993,744 6/1965 Great Britain ..44/62Primary Examiner-Daniel E. Wyman Assistant Examiner-W. J. ShineAttorney-Pearlman and Stahl and Roy J. Ott

[57] ABSTRACT 9 Claims, N0 Drawings FUEL OIL COMPOSITIONS CONTAINING AMIXTURE F POLYMERS TO IMPROVE THE POUR POINT AND FLOW PROPERTIESBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to petroleum distillate oils containing a combinationof polymeric additives which synergistically improve the pour point andflow characteristics of the oil. More particularly, the invention isconcerned with middle distillate fuel oils containing (1) polymers ofethylene with vinyl esters of saturated monocarboxylic acids and/oralkyl esters of ethylenically unsaturated mono or dicarboxylic acids and(2) low molecular weight hydrocarbon polymers selected from the groupconsisting of homopolymers of ethylene, copolymers of ethylene with C Calphaolefins and combinations thereof.

2. Description of the Prior Art Mineral oils containing paraffin waxtherein have the characteristics of becoming less fluid as thetemperature of the oil decreases. This loss of fluidity is due to thecrystallization of the combined wax into needle-like crystals whicheventually form a spongy mass entrapping the oil therein.

It has long been known that various compositions act as wax crystalmodifiers when blended with waxy mineral oils. These compositions modifythe size and shape of wax crystals in such a manner as to permit the oilto remain fluid at a lower temperature. They are known to the art aspour point depressors or pour depressants in that they lower thelimiting temperature at which the oil maintains its free flowcharacteristics.

Various pour point depressants have been described in the literature andmany of these are in commercial use. For example, U.S. Pat. No.3,048,479 teaches the use of copolymers of ethylene and C C vinylesters, e.g., vinyl acetate, as pour depressants for fuels, specificallyheating oils, diesel and jet fuels. Similarly, U.S. Pat. Nos. 3,087,894;3,093,623; 3,13 1,168 and 3,250,714 disclose hydrocarbon oils containingas a pour depressant an ethylene-vinyl acetate copolymer essentially ofthe same type described in said U.S. Pat. No. 3,048,479.

Hydrocarbon polymeric pour depressants based on ethylene and higheralpha-olefins are also well known in the art. For example, British Pat.No. 993,744 teaches the use of copolymers of ethylene with C C olefinsas flow improvers for distillate fuel oils. Similarly, British Pat. No.1,068,000 discloses that the pour point of furnace oils may be improvedby incorporating therein a copolymer of ethylene and propylene.

While these ethylene-ester copolymers and ethylene-alphaolefincopolymers per se are known in the art, it has not heretofore been knownthat mixtures of these two types of polymers exhibit an enhancedcoaction in middle distillate mineral oils containing paraffin wax.

SUMMARY OF THE INVENTION It has now been found, in accordance with thisinvention, that by incorporating in a mineral distillate oil, as flowimprovers, the combination of l) a polymer of ethylene with a vinylester of a C C monocarboxylic acid and/or a C C alkyl ester of anethylenically unsaturated mono or dicarboxylic acid and (2) ahydrocarbon polymer selected from the group consisting of homopolymersof ethylene, copolymers of ethylene with C C alpha-olefin, andcombinations thereof, a synergistic improvement in the flow propertiesof the oil over that provided by the incorporation of either of thesetwo types of polymers alone is obtained.

The ethylene-vinyl ester polymers used in the synergistic mixture of theinvention contain about 3 to 40, preferably 4.6 to 18, molar proportionsof ethylene per molar proportion of a vinyl alcohol ester of a C Cmonocarboxylic acid. These polymers are generally well known in the art,being described in U.S. Pat. Nos. 3,048,479; 3,087,894; 3,093,623 and3,250,714, which patents are incorporated herein in their entirety byexpress reference thereto. Specific examples of these vinyl estersinclude vinyl acetate, vinyl propionate, vinyl isobutyrate, etc. Thepreferred vinyl ester is vinyl acetate.

The polymers prepared from ethylene and aliphatic esters ofethylenically unsaturated monocarboxylic acids will contain about 3 to40, preferably 4.5 to 20, molar proportions of ethylene per molar amountof an ethylenically unsaturated ester having the general formula:

wherein X is a hydrogen atom or a lower alkyl group of l to 7 carbons,e.g., methyl, ethyl, propyl, etc. and Y is:

wherein R is a C, to C preferably C to C straight or branched chainalkyl group. Of these the acrylates and methacrylates are preferred.Such esters include methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, isopropyl acrylate, isobutyl acrylate, COxo acrylate, isobutyl methacrylate, lauryl acrylate, C Oxo methacrylateand the like. A further description of these polymers prepared fromethylene and the aforedescribed ester monomers may be found in U.S. Pat.No. 3,126,364 and Canadian Pat. No. 676,875, which patents areincorporated herein in their entirety by express reference.

Component (1) of the synergistic mixture of the invention also includesthose polymers comprised of 3 to 40, preferably 4.5 to 20, molarproportions of ethylene per molar proportion of a C C mono or diesterhaving the general formula:

wherein each R is hydrogen or methyl, and wherein R is hydrogen or a C Cstraight or branched chain alkyl group. Anhydrides of the correspondingacids may also be employed. It is preferred, however, to use thediesters of fumaric and maleic acid. Examples of such materials includeboth cis and trans compounds such as maleic anhydride; dimethyl maleate;diethyl fumarate; methyl, ethyl fumarate; diisopropyl fumarate,di-(n-pentyl) fumarate; di-(C Oxo) fumarate; dilauryl maleate; the monomethyl ester of fumaric acid, i.e., one R is hydrogen and the other ismethyl; the mono n-octyl ester of maleic acid; etc.

The Oxo alcohols mentioned above are isomeric mixtures of branched chainaliphatic primary alcohols prepared from olefins, such as polymers andcopolymers of C to C monoolefins, reacted with CO and hydrogen in'thepresence of cobalt-containing catalyst such as cobalt carbonyl, attemperatures of about 300 to 400 F., under pressures of about 1000 to3000 psi., to form aldehydes. The resulting aldehyde product is thenhydrogenated to form the 0x0 alcohol which is then recovered bydistillation fromthe hydrogenated'product.

The aforedescribed ethylene-ester polymers which form component (1) ofthe synergistic mixture of this invention are prepared in accordancewith well-known techniques. For example, polymerization of the ethyleneand vinyl ester canbe carried out as follows: Solvent and a portion-ofthe vinyl ester, e.g., 0-50 weight percent, preferably 10 to 30 weightpercent, of the total amount of unsaturated ester used in the batch, arecharged to a stainless steel pressure vessel which is equipped with astirrer. The temperature of the pressure vessel is then brought to thedesired reaction temperature, e.g., 70 200 C., and pressured to thedesired pressure, 500 10,000 psig., with ethylene. Then catalyst,preferably dissolved in solvent so that it can be pumped, and additionalamounts of unsaturated ester are added to the vessel continuously, or atleast periodically, during the reaction time, e.g., l-5 hours, whichcontinuous addition gives a more homogeneous copolymer as compared toadding all the unsaturated ester at the beginning ofthe reaction. Alsoduring this reaction time, as ethylene is consumed in the polymerizationreaction, additional ethylene is supplied through a pressure controllingregulator so as to maintain the desired reaction pressure fairlyconstant at all times. Following the completion of the reaction, theliquid phase of the pressure vessel is distilled to remove the solventand other volatile constituents of the reacted mixture, leaving thepolymer as residue.

Usually, based upon 100 parts by weight of the ester copolymer to beproduced, about 100 to 600 parts by weight of solvent, and about 1 to 20parts by weight of a free radical initiator will be used to catalyze thereaction.

The solvent can be any non-reactive organic solvent for furnishing aliquid phase reaction which will not poison the catalyst or otherwiseinterfere with the reaction, and preferably is a hydrocarbon solventsuch as benzene and hexane.

Free radical initiators that can be used include acyl peroxides of C, toC branched or unbranched, carboxylic acids such as: di-acetyl peroxide,di-propionyl peroxide, di-pelargonyl peroxide, di-lauroyl peroxide, etc.The lower acyl peroxides such as di-acetyl and di-propionyl peroxide areless preferred because they are shock sensitive. Other free radicalinitiators that can be used include di-tert. butyl peroxide, benzoylperoxide, various azo initiators such as azodiisobutyronitrile andazobis Z-methylvaleronitrile, etc.

The ethylene-alkyl ester polymers of this invention are prepared in amanner similar to the ethylene-vinyl ester copolymerization describedabove. Additional preparation methods are adequately described in theliterature and may be found, for example, in US. Pat. Nos. 2,327,705;3,048,479; 3,087,894; 3,093,623; 3,126,364; 3,165,485 and Canadian Pat.No. 676,875.

Component (2) of the synergistic mixture of this invention is ahydrocarbon polymer which is a homopolymer of ethylene or a polymercomprised of about 55 to 100 mole percent ethylene and to 45 molepercent of C to C alphamonoolefin (including mixtures thereof) havingthe general formula: H C CHR wherein R is a linear or branched alkylgroup containing 1 to 16 carbon atoms. Specific examples of thesealpha-monoolefins include propylene, isobutene, n-octene-l, isooctene-l,n-decene-l, dodecene-l, and the like. The preferred hydrocarboncopolymer is a copolymer containing 74 to 95 mole percent ethylene and 5to 26 mole percent propylene. Homopolymers of ethylene when prepared byfree radical catalysis are also preferred. A further description ofthese hydrocarbon polymers is given in British Pat. Nos. 993,744 and1,068,000, which patents are incorporated herein in their entirety byexpress reference.

The hydrocarbon polymers of the synergistic mixture of the invention areconventionally prepared by homopolymerizing ethylene or by polymerizingethylene with a C C alphaolefin or a mixture of said alpha-olefins inthe presence of a conventional Ziegler-type catalyst or a free radicalcatalyst such as those described above. Methods for polymerizing theseolefin monomers are adequately described in the literature, e.g.,British Pat. Nos. 993,744 and 1,068,000.

The polymers of the synergistic mixture (i.e., component 1 and component2) will have number average molecular weights in the range of about 850to 50,000, preferably about 1,250 to 7,500, as measured by Vapor PhaseOsmometry (V- P0).

The synergistic composition of the invention comprises from about 1 toabout 99 percent by weight of the aforedescribed ethylene-ester polymerand from about 99 to about 1 percent by weight of the aforedescribedhydrocarbon polymer. Preferred proportions are admixtures comprisingfrom about 25 to about 75 weight percent of the ethyleneester polymerand from about 25 to about 75 weight percent of the hydrocarbon polymer.Usually the synergistic mixture will be used as a 50/50 weight percentcomposition of the two types of polymers.

The synergistic mixture of the invention will generally be added tohydrocarbon oils in amounts of 0.005 to 2.0 weight percent, preferably0.01 to 0.2 weight percent, said weight percent being based upon theweight of the oil to be treated.

For ease in handling, the synergistic mixture of the invention may beutilized in a concentrated form. For example, to facilitate storage andtransportation, the aforedescribed synergistic mixture may be blendedwith a hydrocarbon solvent, e.g., a mineral oil, hexane, toluene, etc.,to form a concentrate comprising from about 20 to about weight percenthydrocarbon solvent, preferably 40-60 weight percent, and from about 20to about 80 weight percent of the synergistic mixture, preferably 40-60weight percent.

The hydrocarbon oils, which are blended with the synergistic mixture ofthis invention, include distillate fuel oils such as cracked or virginor mixtures thereof, middle distillate fuels boiling in the range of 250to 750 F., such as heating oil, diesel fuel oil, etc.

The synergistic composition of the invention is found to be compatiblewith other additive materials and may be blended successfully withdistillate oils containing minor amounts of viscosity index improvers,other pour depressants, rust inhibitors, antioxidants, sludgeinhibitors, sludge dispersants, etc.

The invention will be further understood by reference to the followingexamples which include preferred embodiments of the invention.

EXAMPLE 1 The synergistic improvements obtained by adding theaforedescribed components (1) and (2) in accordance with the presentinvention are illustrated in two different middle distillate heatingoils which are known to be relatively nonresponsive or poorly responsiveto the addition of pourdepressing and flow improving additives. Theseoils are hereinafter called Oil A and Oil B and their physicalproperties are set out below in Table i.

In this Example, oil Compositions containing components (1) and (2) ofthe synergistic mixture of this invention were tested in a Fluidity Testwhich involves placing a 40 milliliter sample of the oil composition tobe tested into an hour-glass shaped device having upper and lowersections which are transparent plastic cylinders having an innerdiameter of 3.8 centimeters and being connected by a brass capillaryhaving a length of 12.5 millimeters and an inner diameter of 2.25 millimeters. The lower section is covered by a thin aluminum disc. The oilin the tester is placed in a cold box and is cooled from a point F.above the cloud point to 10 F. below the cloud point at a rate of 4F./hr. The tester is inverted and allowed to settle for 1 minute. Thenthe aluminum disc is punctured so that the oil flows from the upperchamber through the capillary tube into the lower chamber. A pass isconsidered when 90 percent or more volume of the oil flows from theupper chamber to the lower chamber in a time of 3 minutes or less. Thetest results are reported as Percent Fluid which designates the percentof the test composition which has flowed into the lower chamber in atime of 3 minutes. In this connection, it has been found that a percentfluid value of 90 percent or more will perform well under winter fieldconditions, while those with 48 to 75 percent fluid would givelineplugging under the same conditions.

Table II which follows summarizes the Fluidity Test results for Oil Acontaining synergistic mixtures of the invention.

TABLE II Fluidity of Synergistic Mixtures in Oil A Copolymer containing69 wt. 2: ethylene and 3! wt. vinyl acetate, having a number averagemolecular weight (VPO) of 2,605 and prepared in accordance with themethod ofu.S. Patent 3,048,479.

Copolymer containing 89 wt. ethylene and ll wt. 96 propylene, having anumber average molecular weight (VPO) of L495 and prepared in accordancewith the method ofBritish Patent 993,744.

Copolymer containing 61 wt. ethylene and 39 wt. 1: isobutyl acrylate,having a number average molecular weight (VPO) of 3,368 and prepared inaccordance with the method ofU.S. Patent 3,048,479.

As shown by Table II, the combination of the polymeric additivecomponents of this invention imparts a marked improvement over thatwhich could be obtained by the use of an equivalent amount of eithermaterial alone.

EXAMPLE 2 The ability of the polymeric components of this invention tosynergistically improve the flow characteristics of middle distillateoils was further demonstrated in a Flow and Plugging Test. In this test,a 3,500 milliliter sample of the oil to be tested is placed in a 1gallon can and cooled to a temperature 5 below the cloud point of thebase fuel over 8 hours and maintained at this temperature for 7 hours.The cooled sample is then drawn under vacuum through a length of coppertubing having a conical inlet. The conical inlet serves as a wax packingdevice which increases the severity of thetest as far as plugging theline is concerned. The flow rate through the copper tubing is a measureof the effect of the viscosity of the fuel, and, thus, an indication ofits flow behavior.

In this test, the copper tubing which was inserted in the cooled fuelsample measured 150 centimeters in length with an outside diameter of4.8 millimeters and a wall thickness of 0.8 millimeters and was fittedwith an inlet machined from a 1 inch brass cube to a right angle cone 1inch in diameter at the base and having at the top where it joins thecopper tubing an orifice of one-sixteenth inch in diameter and onesixteenth long. The fuel was drawn into and through this line under 5inches of mercury vacuum, and measured in a suitable receiver.

A pass is 90 percent or more of the sample flowing with a drop in thevacuum at the end of the test (signifying no wax plug in the line). If aplug occurs at the inlet, it is released by increasing the vacuummomentarily or with a wire. A borderline result is at least 90 percentover with one wax plug at the end or during the test. A failure is lessthan 90 percent over, or two wax plugs. The results for Test Oil Bcontaining the ethylene-vinyl acetate copolymer of Example 1, theethylenepropylene copolymer of Example 2 and a 50/50 mixture thereof aregiven in the following Table.

TABLE III Evaluation of Additive Mixtures in Flow and Plugging TestsTest rating Flow rate ml./rnin.

Additive blended with oil B Fluid in test Plugging tendency Fail 9] 99Pass 92 137 Pass From the data in Table III, the synergistic effectprovided by the combination of the ethylene-vinyl acetate copolymers andethylene-propylene copolymers is evident. Thus, the combination of theadditive components of this invention impart an improvement in flowcharacteristics which is greater than that which could be obtained bythe use of an equivalent amount of either material alone.

It is not intended that this invention be limited to the specificexamples presented by way of illustration. The scope of the invention islimited only by the appended claims.

What is claimed is:

1 An oil composition comprising a major proportion of a petroleumdistillate fuel boiling in the range of 250 to 750 F. and about 0.005 to2.0 weight percent of a synergistic mixture containing (a) 1-99 parts byweight of an oil-soluble polymer comprised of about 3 to 40 molarproportions of ethylene per molar proportion of a compound selected fromthe group consisting of a vinyl alcohol ester of a C to C monocarboxylicacid; an ethylenically unsaturated ester having the formula:

b t-owherein each X is a hydrogen atom or a lower alkyl group and Y is:

wherein each R is a C to C alkyl group; and (b) l-99 parts by weight ofan oil-soluble polymer comprised of about 74 to 95 mole percent ethyleneand 5 to 26 mole percent of C, to C alpha-monoolefin; said polymershaving number average molecular weights ranging up to about 850 to50,000.

2. An oil according to claim 1, wherein said component (a) is a polymercomprised of ethylene and vinyl acetate.

3. An oil according to claim 1, wherein said component (a) is a polymercomprised of ethylene and an ethylenically unsaturated ester having theformula:

wherein X is a hydrogen atom or methyl and Y is:

wherein R is a C to C alkyl group.

4. An oil according to claim 2 wherein said component (b) is a copolymerof ethylene and propylene.

5. An oil according to claim 2 wherein said component b) is a copolymerof about 74 to 95 mole percent ethylene and about 5 to 26 mole percentpropylene and said oil-soluble polymers have number average molecularweights within the range between about 1,250 and 7,500.

6. A composition according to claim 2 wherein said ethylenicallyunsaturated ester component is isobutylacrylate.

7. An oil composition comprising a major proportion of a petroleumdistillate fuel boiling in the range of 250 to 750 F. and about 0.005 to2.0 weight percent of a synergistic mixture containing (a) anoil-soluble polymer comprised of about 4.6 to 18 molar proportions ofethylene per molar proportion of vinyl acetate; and (b) an oil-solublepolymer comprised of about 74 to 95 mole percent ethylene and about 5 to26 mole percent of propylene; said polymers having number averagemolecular weights within the range between about 1250 and 7500.

8. A concentrate comprising from about 20 to about wt. of a hydrocarbonsolvent and from about 20 to about 80 wt. of the synergistic mixturedefined by claim 1.

9. A concentrate comprising from about 20 to about 80 weight percent ofa hydrocarbon solvent and from about 20 to about 80 weight percent ofthe synergistic mixture defined by claim 2.

2. An oil according to claim 1, wherein said component (a) is a polymercomprised of ethylene and vinyl acetate.
 3. An oil according to claim 1,wherein said component (a) is a polymer comprised of ethylene and anethylenically unsaturated ester having the formula: wherein X is ahydrogen atom or methyl and Y is: wherein R is a C1 to C14 alkyl group.4. An oil according to claim 2 wherein said component (b) is a copolymerof ethylene and propylene.
 5. An oil according to claim 2 wherein saidcomponent (b) is a copolymer of about 74 to 95 mole percent ethylene andabout 5 to 26 mole percent propylene and said oil-soluble polymers havenumber average molecular weights within the range between about 1,250and 7,500.
 6. A composition according to claim 2 wherein saidethylenically unsaturated ester component is isobutylacrylate.
 7. An oilcomposition comprising a major proportion of a petroleum distillate fuelboiling in the range of 250* to 750* F. and about 0.005 to 2.0 weightpercent of a synergistic mixture containing (a) an oil-soluble polymercomprised of about 4.6 to 18 molar proportions of ethylene per molarproportion of vinyl acetate; and (b) an oil-soluble polymer comprised ofabout 74 to 95 mole percent ethylene and about 5 to 26 mole percent ofpropylene; said polymers having number average molecular weights withinthe range between about 1250 and
 7500. 8. A concentrate comprising fromabout 20 to about 80 wt. % of a hydrocarbon solvent and from about 20 toabout 80 wt. % of the synergistic mixture defined by claim
 1. 9. Aconcentrate comprising from about 20 to about 80 weight percent of ahydrocarbon solvent and from about 20 to about 80 weight percent of thesynergistic mixture defined by claim 2.